The transmission of optical signals for data communication conventionally involves encoding the signals onto a carrier beam at a transmitter, injecting the beam through a low-loss transmission medium, and decoding the signals from the beam at a receiver. The carrier beam is composed of a series of optical waves or pulses. The beam easily propagates through the transmission medium because the medium is optimized for low-loss (i.e., low scatter and absorption), low dispersion and zero near-resonance loss at the wavelength the beam is generated. The most common example of such medium is optical fiber cables used by the telecommunication industry in long distance transmission systems. Such long distance transmission systems typically use these optical fibers with LEDs or laser diodes to generate carrier beams at infra-red wavelengths.
A significant drawback of these conventional optical signal transmission systems is that they cannot efficiently transmit optical signals through non-optimized transmission media due to high signal loss from absorption in the media. Such non-optimized transmission media may be smoke filled air, or atmospheric conditions, like fog. These types of media are generally considered impractical for existing optical transmission systems.
Another drawback of these conventional transmission systems is that they are limited to optical signals in a relatively small set of frequencies, since the transmission media are optimized to be highly non-absorbing in the particular range of infra-red wavelengths available from low-cost laser diodes.